We propose to develop and test a bundled rapid HIV/HCV testing intervention (joint offer of HIV and HCV testing at the point of service), whose aim is to increase the receipt of rapid HIV and rapid HCV test results among patients of drug abuse treatment programs. Over 1.1 million people in the U.S. are living with HIV, 3.2 million are living with HCV and an estimated 25% of persons living with HIV also have HCV. Substance-using populations are at higher risk of infection or transmission of HIV and HCV. Among those infected, nearly twenty percent are unaware that they are infected with the HIV virus and less than half of the people living with HCV are aware of their infection. HIV co-infection complicates the treatment and management of HIV, and is also associated with considerable increase in risk for liver disease and liver-related deaths from HCV. It is therefore of great public health importance to ensure the prompt diagnosis of both HIV and HCV among those who face the highest burden of both diseases. Unfortunately, the proportion of drug treatment programs offering HIV testing has declined over time. Even fewer treatment programs offer HCV testing. The introduction of rapid HIV and (more recently) HCV rapid testing presents a promising approach to reversing these trends. Furthermore, advances in treatment of HIV and the advent of more effective treatment for HCV necessitates the urgent need for effective comprehensive approaches that promote early detection, knowing one's infection status, and early linkage and initiation of care. The objectives of the proposed feasibility study are thus to: 1) collect acceptability and implementation data and develop a bundled rapid HIV and HCV testing strategy to facilitate the timely diagnosis of both HIV and HCV among drug-abusing populations; and 2) design a multi-component framework to promote the adoption and sustainability of the bundled testing strategy in drug treatment programs. To do so, we will extend the ADAPT-ITT model, a sequential eight-phased method for adapting evidence-based HIV interventions, to include the addition of multi-disease components (inclusion of HCV). Using a rigorous process of adaptation involving patients, providers, and treatment program managers, ADAPT-ITT will be used to adapt an evidence-based HIV intervention for the proposed bundled rapid HIV/HCV testing strategy. We will then test, in a randomized control trial, the extent to which bundled testing increases receipt of rapid HIV and rapid HCV test results after one month. Secondary outcomes will include medical records validated receipt of results, linkage to care, reported sexual risk behaviors and drug use practices after 3 months. We will conduct formative research on the barriers and facilitators of the adoption, implementation, and sustainability of the bundled testing strategy in drug treatment programs. Results from the proposed developmental and pilot activities will inform a multi-component multi-level intervention cluster-randomized trial for an R01.The bundled rapid HIV/HCV testing strategy, if found to be effective, will have far-reaching benefits beyond drug abuse treatment program, including health care settings with limited resources and competing demands.